In fluid transfer systems, it is frequently necessary to flush the input end of the system to cleanse that end from filtered impurities, infectious bacteria, or other substances which might tend to contaminate the system. Such systems typically include an assembly for conducting a fluid from the input end to an output end, to a collection or receiving tank and through a main fluid flow line. In such systems, a flushing conduit intersects the main fluid flow line proximate the input end. A flushing agent such as water or sanitizing agent is introduced into the main line through the flushing conduit in order to flush out the contaminating substance.
Illustrative of such a system is an automatic milking device which is typically used on dairy farms. Such a system has, at its input end, a milking claw which has a plurality of teat cups, each of which is attachable to one of the teats of a cow's udder. Vacuum is applied to the cups to draw milk from the udder and into the main milk flow line. The main line, thereafter, conducts the milk to a receiving, holding, or storage tank.
Flushing is desireable with this kind of system because of a condition known as mastitis. This condition is caused by a microorganism known as the streptococcus hemolyticus and can be prevalent among the cows of a dairy herd. The condition spreads fairly easily among the herd and is transmitted from one cow to another when the milking claw of an automatic milking machine is attached to the udder of a healthy cow after being used on a cow infected with mastitis.
A number of strains of mastitis are known. One particular strain, although affecting the cows in a cattle herd, has no effect on humans. Milk from a cow infected with this strain may, therefore, yet meet standards for human consumption and can be allowed to flow into a storage tank containing milk to be pasteurized and processed in other manners for human consumption.
Another strain can, if ingested by humans, cause septic sore throat. Even when a number of cows in a diary herd are infected with this strain, however, it is necessary to draw milk from the infected cows at regular intervals. Typically, the easiest way that this can be accomplished is by milking the infected cows at the same intervals as are milked the healthy cows. The milking can even be accomplished using the same automatic milking device in the case of both healthy and infected cows.
Milk drawn from an infected cow cannot, of course, be allowed to flow into the tank in which is stored milk to be processed from human consumption. Intermingling can be prevented by disconnecting the output end of the main milk flow line from the tank whenever the milking device is attached to the udder of an infected cow.
Such methods prevent contamination of the wholesome milk, but the problem of transmitting mastitis from an infected cow to a healthy cow remains. In order to preclude transmission of the disease, the milking claw is flushed after completion of use on a particular cow. Various solutions and sanitizing agents can be used for this purpose. Typically, the claw is first flushed by allowing water to flow through the flushing conduit and out through the claw, and then flushing the claw with a sanitizing agent. Prior to attaching the claw to the next cow to be milked, it is again flushed with water so that none of the sanitizing agent will be allowed to contaminate the wholesome milk.
During backflushing operations, the main milk flow line is closed off so that flushing fluid introduced through the flushing conduit into the main line can flow only in the direction of the milking claw and out through the teat cups.
Prior art structures have been designed to accomplish flushing of the milking claw as desired. One such structure is shown and described in U.S. Pat. No. 4,168,677 issued to Michael J. Brown on Sept. 25, 1979. This patent is for a Sanitary Backwashing System for Automatic Milking Machines. The structure of that patent includes a three-way control valve which is mounted in the main flow conduit. The control valve includes a movable valve core disposed within the interior of the valve housing. The core includes a network of passageways, and it is rotatable to align various of the passageways as desired to effectuate fluid flows in a particular manner. A main passageway extends through the valve and can be aligned with up-flow and down-flow portions of the main milk flow line to complete a discontinuity in the main line. With the valve in this position, milk drawn from a cow by the milking claw will be transferred directly to a collection tank. When the core is rotated 90 degrees in one direction, alignment of passageways is such that flushing agents can flow from their various reservoirs to the milking claw. With a particular alignment of passageways designed to accomplish this function, a downflow portion of the main milk line will be occluded so that milk in the collection tank cannot become contaminated by the various agents.
The structure of that patent does not, however, provide any means for positively stopping off flow through the down-flow portion of the main milk line when the sanitizing agent is accomplishing flushing. Consequently, if the core were rotated 90 degrees in the wrong direction, the sanitizing agent could, conceivably, flow directly to the wholesome milk thereby contaminating it.
Additionally, the structure of that patent includes a sophisticated sequencing device for regulating the flow of water and sanitizing solution to the milking claw. Because of the intricacy of the sequencing system, more opportunities exist for malfunctioning of the various flushing functions.
It is to these deficiencies in the art that the invention of the present application is directed. The backflushing system of this application both positively precludes contamination of wholesome milk stored in a tank in which it is received, by the flushing agents and, simultaneously provides a simple mechanical sequencing system which virtually precludes malfunction.